Recently, light up-conversion devices have attracted a great deal of research interest because of their potential applications in night vision, range finding, and security, as well as semiconductor wafer inspections. Early near infrared (NIR) up-conversion devices were mostly based on the heterojunction structure of inorganic semiconductors, where a photodetecting and a luminescent section are in series. Fabrication of infrared IR-to-visible up-conversion devices based on inorganic compound semiconductors is challenging because of the lattice mismatch between the two types of semiconductor materials used for photodetectors and light-emitting diodes LEDs. Because of the high cost of epitaxial grown inorganic devices, inorganic devices have been restricted to fabrication of small area applications.
Other up-conversion devices tend to display efficiencies that are typically very low. For example, a NIR-to-visible light up-conversion device that integrates a LED with a semiconductor based photodetector has exhibited a maximum external conversion efficiency of only 0.048 (4.8%) W/W. More recently, a hybrid organic/inorganic up-conversion device, where an InGaAs/InP photodetector is coupled to an organic light-emitting diode (OLED), has displayed an external conversion efficiency of 0.7% W/W. Currently inorganic and hybrid up-conversion devices are expensive to fabricate and the processes used for fabricating these devices are not compatible with large area applications. Efforts are being made to achieve low cost up-conversion devices with high conversion efficiencies, high sensitivity, high gain, and high image fidelity. Additionally, a device where the IR irradiation enters from a one face and light exclusively exits from a second face is desirable for many applications such as night vision applications.